Aircraft structural limit indicator



Feb. 8, 1949. w, L, R Y 2,461,210

AIRCRAFT STRUCTURAL LIMIT INDICATOR Filed-June 27, 1945 I 3 Sheets-Sheet 1 IN VEN TOR.

ATTORNEY w. GRAY $461,210

AIRCRAFT STRUCTURAL LIMIT INDICATOR 3 Sheets-Sheet 2 Feb. 8, 1949.

Filed June 27 1945 I I I I I (\l w L| I I N I I ll I I, I I I I I I I I I I I I I I I I 2 INVENTOR.

ATTORNEY Feb. 8, 1949. AY 2,461,210

AIRCRAFT STRUCTURAL LIMIT INDICATOR Filed June 27, 1945 5 Sheets-Shet 3 mmvrox.

ATTORNEY designed. It is therefore thought to be apparent that if a means is provided for indicating on the diagram 5, both the instant airspeed and the acceleration being placed upon the craft in flight, when the intersection 84 of the indcators 32 and 83 fall within the shaded area 9, the pilot may well assume that he is operating the craft within its structural design limits. As a means of furnishing such an indicating means, the following described structure is provided within. the case The air speed indicating portion of the device includes the following described apparatus. An aneroid bellows I which is disposed within the case and which has its end portion rigidly mounted with relation to the case. An air pressure or pitot tube |2 leads from the case I, and has an open end, not shown, which is disposed exteriorly of the craft facing toward the front thereof so that air is rammed into the tube and bellows by relative-motion between the aircraft and the surrounding The length of the bellows varies in accordance with the internal pressure created by the rammed air, in the usualmanner. The bellows ID has a closed end |3 to which is attached a projecting ear l4. Adjacent to, but to one side of the path of travel of the closed end 13 of the bellows, there is provided a vertical shaft l5. The shaft I5 is journalled for rotation in suitable bearings, not shown, but which are carried by the adjacent wall of the case I. A'horizontal arm l6 has one of its ends rigidly attached to the shaft I5 by a key l1, and its other end is pivotally engaged around a pivot pin 8 carried by one end of a link Hi. The other end of the link I9 is pivotally connected to the ear H by a pin 20. A horizontally disposed arm 2| has one of its ends rigidly attached to the shaft I5 by a key 22, and its other end carries a gear segment 23. Obviously, longitudinal expansion of the bellows |0 acts to move the closed end l3, the ear I4 and the link I9, and such movement causes the arm IE to partially rotate the shaft l5. Also, partial rotation of'the shaft |5 acts to move the arm 2| in an arcuate horizontal path which similarly moves the gear segment :23.

The air speed indicator mechanism further includes a pulley 24 and gear 25 both of which surround and are keyed to a vertically disposed shaft 26. The shaft 26 is journalled for rotation in suitable bearings, not shown, carried by the case and the gear 25 is in meshed engagement with the gear segment 23.

Within the case and at each side of the rear face .3 thereof, there are provided vertically disposed shafts 21. Each of the two shafts 21 carries two rigidly mounted pulleys located adjacent opposite ends of the shafts 21. The two upper pulleys are indicated by the two reference numerals 28, and the lower pulleys by the numerals 29. The ends of the two shafts 21 are journalled for rotation in bearings, not shown, carried by the case An endless wire or cable 30 is engaged around the two upper pulleys 28,. so that they must rotate in unison. r A second endless cable 3| extends substantially around the pulley 24, and continues from there toengage the outer surfaces of the two lower! pulleys 29 carried by the shafts 2'l, as more clearly shown in Fig. 4. The cable 3| is so arranged that rotative movement of the pulley. in one direction will cause ,rotation of the pulleys 29 in an opposite direction. In other words, anti-clockwise movement of the pulley 24 willcause left hand travel of that portion of the Cable 3| which extends directly between the two pulleys 29 adjacent the rear face 3, and vice versa.

Extending between and attached to vertically aligned points on the two cables 39 and 3|, is a vertically disposed air speed indicating rod 32. The rod 32 is located sufficiently close to the transparent face 3 of the case that it is readily visible therethrough.

Fromv the above description and by reference to Fig 2 of the drawingsit is apparent that extending movement of the closed end ll of the bellows it! will cause clock-wise movement of the pulley 24, and such movement of the pulley 24 will likewise cause movement of the indicating rod 32 to the rightacross the face of the diagram 5. Contraction of the bellows, will, of course, cause a left hand movement of the rod 32. mm also apparent that. the rod 32 will be moved in either direction a distance which is a function of the air speed of the craft. The comparative diameters of the pulley 24 and pulleys 2a, the pitch radii of gears 23 and 25, and the ratio of lengths of the arm l6 and 2| are such that the velocity indicating rod 32 may be moved substantially across the end 3 of the case by expansion and contraction of the bellows H1. The vertical graduation lines, indicated by the row 8 of numerals, are so correlated with the possible travel of the indicating rod 32, that all of the probable air speeds of the craft in flight may be indicated by the rod 32.

As stated hereinabove, the device further ineludes mechanism for indicating the magnitudes of acceleration, relative to a specific axis of the aircraft, to which it is subjected while in operation. This mechanism includes the following described parts.

Journalled for-rotation in the case in suitable bearings, not shown, there is provided a horizontal shaft 40 which is perpendicular to the center line of the craft, and upon which are rigidly keyed gears 4| and 42. Also keyed to the shaft 40 is one end of an arm 43 which carries, at its other end, a weight 44. The arrangement is such that the weight 44 may swing in a vertical plane with the shaft 49 acting as a pivotal axis. One end of the shaft 4|] is rigidly attached by a coupler 45 to a torsion spring 46, the other end of which is rigidly attached by a fitting 41 to a wall of the case The torsion spring 46 resiliently and elastically resists rotation of the shaft 40 inboth directions. The arm 43 is therefore normally maintained in a position substantially parallel to the longitudinal axis of the aircraft.

Pivotally mounted in the housing in suitable bearings, not shown, is a short horizontal shaft 48. (see Fig. 3) which is keyed to a gear 49 meshing with the teeth of the gear 4|. Also keyed to the shaft 48 is one end of an arm 59, the other end of which carries a weight 5|. The weight 5| weighs the same as does the weight 44 and acts as a counterbalance to .the weight 44 when the weight 5| is acted upon-by a vertical acceleration normal to the longitudinal axis of the craft oppositely directed to the acceleration to which the weight 44- is subjected, or when the weights are both subjected to the same accelerations which areparallel to the longitudinal axis of the aircraft and the weights 44 and 5| are deflected to positions such that the arms 43 and 50 respectively are not substantially parallel to the longitudinal axis of the aircraft.

The inherent strength of the spring 46 to resist rotation of the shaft is such, compared to the weight of the objects 44 and 5|.that the arms 43 and so will remain in a substantially horizontal causes no me to the long-imam l axis-df' thea aim 3 aiid' tfie wight- 4A and bath-sameness extend '-"-i fidi1ctiohs parallel to the longitudinal aiti's 'iif 'the' craft, and parallel to the Wing span er aft. I g

mounting arrangementbf'the twc weigiits u-- rissuch-th-at ate-fly tiiiie "theemitcefiioiinal to both I the loii-gitudinai axis of t; mete messes-wise axis of the 'erait theweights-will be moved frin their rise-ma prevesisw of ph-ys'ics tliaflbodie's' mastitis tend to remain otion jiii-les's"disturbed by terfialfbi'ce. shame the ship while in straight flight suddenly be .put into a steep bank, or a dive,

or should its niisesuddenly be turned upwardly, the tendency of the weights will be to continue to travel in their original paths in space. Since the position of the case I in space changes with the position ofthebody of the ship in space, the po sltionsof the weights will change with relation to the longitudinal axis of the shipy'aii'd consequently'ii ith relation to the case i. 'If the ship-in li-igh s'fid lvel flight is suddenly put in a 'bank r intoa cli'mb, the force of inertia causes he weights to try to continue in a stiaight line; they W111 actually do so to some extent. Since he filaEiie and instrument case have a ctuall-y meted iifii'lifald-withrelation to their fol iner pathfthe weightsmove downward-in the-ease. As- -soen as the airplane has resumedstraigh-t line flight, regardless of direction; the weights assume stationiifW-positions near their original horizontal attitude of the airplane, the spring, and the effect of gravity. Should a ship in level flight suddenly be nosed down, the force of inertia which causes the above described movement of the weights is actually very similar to centrifugal force. (Same physical law governs.) The main difierence is 45 z'siitai fios'itions. in eceeidaiiee the case.

s'liaft 51 retatabiyioumsiieeesteem 7 that tlie' -present deviceg the aiiisramdnd wfiim a, weights will move toward the bottom 7 h In this ase, mtvement ithe weights at u to th additio'nal" tce'ti'gmvity;

g in ve" owi d the tottom similarlyga dow at i-eor'fgiist" merit fithe ifi'ei'tia' Weight's tGNVaII d airplane :is being eieted, secs ion 'd yi maneuvering of the ship tl i fllowiri east-meet mechanism is provided.

Within tam ar t-he mass. The shat EE -is "equipiied jaeerit one en'dWi-th uney ts a the-s1 and pattl-allysu-i round puli'ey i ll Theethef erids'tithe hastens-a1 51 are respect-ii 1y tiovides' w Y eir uiiey and lil. ndless ord oi eabl sz cennets these'twe pulleys 60 a d 61. Obvious'i when the to-partia-lfrtatioby we descrited;

nison Extendingbetvieen'the two cat;

the two shafts 56 and 51 will rot-at estii' andfB'Q" is aheiizeiitai 'iiidiat-in'g red*63,*which is'a-aaetea to tnbve vertically when the ulley 54 is rotated. 'mie iiieiea "rig ans- 63 are -sojldcated exit parallel-planes. V i 7 t-netraiisparefit "ane {which cleses'the-eirwt cf-tneca ef|,-tneyre both Visible ft "lie pilo't; Similarly; since "0th f tlit face of the diagra'rriia heir en ti intersection may ea'siiy be rea-u (iii-the by th pilot. r

shaded area e dftheuiagramor 1 so desi'gfid, that so long as the pcinttof the, interseticn 6f the two dedicating rods remains withinth boundary-line of theshati-e area ,the pilot lio'w's "that e not subject nghis-slants dah'g'e" tions *w-hin wiii cause stresses J b'jidiidits structural-design iiniits.

As stated hereinabove, the diagram 9 is drawn to represent the safe limits of each specific ship or type of, ships in which the instrument is to be installed. It therefore becomes unnecessary to provide different instruments for difierent classes rise of ships, nor is it necessary to mechanically adjust the instrument ,mechanism to accommodate different ships or classes of ships. It is only necessary to provide each ship with a chart, having its shaded area 9 drawn to fit that particular ship or class of ships. '1 Q The chart disclosed herein might well be termed a velocity-gravity diagram. in this case, the word gravityi refers to therelative measure of the force of inertia, in terms of gravity, and not to the force of gravity. This term is widely used throughout the aircraft industry. For instance,-plus 3 Gs on the chart means that the wings and other component parts of the ship are being subject to loads equal to three times the loads to which. they would be subjected during straight normal flight of the craft. (2 Gs) means the ship parts are being subjected to a load in the opposite sense, equal to two times the loads incurred during straight normal flight of the craft.

It is pointed out that by properly calibrating the chart, the mechanism may also be used to give the readings of a stallmeter.

From the above description, and by reference to the accompanying drawings, it is thought an instrument has been disclosed which will accomplish all of the objects and purposes for which it is intended. .The structure shown in the drawlugs, and described hereinabove, only disclose one embodiment of the invention, and might well be subjected to modification and alteration, and I therefore do not limit mystelf to the specific embodiment shown, further than 1am limited by the scope of the appended claims.

I claim: V V

1. An instrument in and for an aircraft, for continuously indicating the simultaneous magnitudes of the accelerations and velocities to which said aircraft is being subjected during operation, comprising: a velocity acceleration diagram on which any point represents a specific velocity and a specific acceleration; a pair of intersecting indicators mutually co-operating to locate a point on said velocity acceleration diagram; means responsive to the velocity of the aircraft and operably connected to one of said indicators for moving the same; and means responsive to the accelerations of said aircraft relative to a specific axis thereof, said means operably-connected to the other of said indicators for moving the same.

2. An instrument in and for an aircraft, for continuously indicating the co-existing magnitudes of the accelerations and velocities to which said aircraft is being subjected duringoperation, comprising: a velocity acceleration diagram on which any point represents a specificvelocity and a specific acceleration; an outline on said diagram defining the combinations of speed and acceleration for which said aircraft was structurally designed; a pair of intersecting indicators mutually co-operating to locate a point on said diagram; means responsive to the velocity of the aircraft and operablyconnected to one of said indicators for operating the same; means responsive to accelerations of said aircraft relative to a specific axis thereof, said means operably connected to the other of said indicators for operat ing the same, the positions of said two indicators However,

with relation to each other and to said diagram being adapted to apprise an occupant; ofthe aircraft as to whether or not the craft is being sub-, jected to combinations of acceleration and velocity beyond its safe structural limits.

3. An instrument in and for an aircraft, for continuously indicating the simultaneous magnitudes of the accelerations and velocities to which said aircraft is being subjectedduring operation, comprising: a velocity acceleration diagram the outline of which defines the safe structural limits to which the craft may be subjected, and on which any point represents a specific velocity and a specific acceleration; a pair of intersecting indicators mutually co-operating to locate a point on said velocity acceleration diagram; means responsive to the velocity of the aircraft and operably connected to one of said indicators for moving the same; and means re.- sponsive to the accelerations of said aircraft relative to a specific axis thereof, said means operably connected to the other of said indicators for. moving the same.

4. An instrument in and for an aircraft'for continuously indicating visually on one diagram the magnitudes of the accelerations and velocities to which said aircraft is being subjected, comprising: a velocity acceleration diagram having two intersecting axes; indicia, indicating aircraft velocity, and dividing one axis of said diagram; indicia, indicating the magnitudes of acceleration, to which the aircraft may be subjected, and dividing the other axis of said diagram; at first indicator co-operating with said diagram and movable with respect to the first mentioned indicia; means afiected by changes in aircraft velocity and operably connected to said first indicator for moving the same; a second indicator also co-operating with said diagram and movable with respect to the second mentioned-indicia; means afiected by changes in acceleration of the aircraft in the direction of a, predeterminedaxis, and operably connected to said second indicator for moving the same, the position of said two indicators with relation to each other and to said diagram being adapted to apprise the observer as to whether or not the aircraft is being subjected to abnormal stresses during flight.

' WILLIAM L. GRAY.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Germany June 6, 1930 

